The invention relates generally to methods and apparatuses for determining particle characteristics, and more particularly, to methods and apparatuses having particle tracking and image analysis logic and force field devices for determining one or more physical cell characteristics.
Cell analysis and separation is an increasingly important technique in the diagnosis and treatment of various cancers and diseases. Of primary importance to cell analysis and separation is the ability to identify, or label, cell properties and characteristics of interest. The identification, or labeling, of cell properties and characteristics allows them to be used as xe2x80x9chandlesxe2x80x9d which, in turn, can be used to separate xe2x80x9clabeledxe2x80x9d cells from other cells. Among the most commonly used labels for sorting cells are immunological labels which include, for example, immunofluorescent and immunomagnetic labels. Immunofluorescent labels typically include, for example, a fluorescent molecule joined to an antibody. Immunomagnetic labels typically include, for example, a paramagnetic compound or molecule joined to either a primary or secondary antibody. Cell labeling is performed by attaching the antibody to a marker of interest on the surface of the cell (i.e., cell surface marker).
However, though extremely sensitive immunological xe2x80x9clabelsxe2x80x9d have been developed which allow for the careful labeling of cells, the potential of these labels for cellular analysis and separation has yet to be fully realized. As a result thereof, the cellular properties and characteristics which these labels are capable of identifying have also yet to be fully analyzed. For example, in the case of immunomagnetic labels, the highly accurate quantification of a cell population""s magnetic susceptibility has been impossible to determine. Additionally, in the general case of immunological labels, the cell surface marker and label density has been difficult to accurately determine.
These deficiencies are due, in large part, to the limitations of analytical devices which are capable of gathering and analyzing the information these immunological labels can provide about cells. Moreover, the lack of qualitative and quantitative knowledge of cell properties and characteristics, such as magnetic susceptibility and cell surface marker and label density, hampers the development of sophisticated cell sorting apparatuses. Accordingly, it is an object of the present invention to provide a method and apparatus for qualitatively and quantitatively analyzing one or more cell characteristics or properties.
According to one aspect of the present invention, apparatuses and methods are provided for quantifying at least one of a plurality of particle physical characteristics. The range of particles includes, for example, cells, cell organelles, platelets, inorganic, organic, biological, and polymeric particles which are optically visible. The plurality of particle physical characteristics include particle size, shape, magnetic susceptibility, magnetic label density, charge separation, dielectric constant, and derivatives thereof. Derivatives include, for example, cell dimensions (e.g., diameter, radius, major axis length, minor axis length, etc.) and optical transmittance. The method includes generating a region of space having a substantially constant force field, determining the velocity of at least one particle within the region by identifying and locating the particle and its coordinates in at least two temporally defined digital images, and determining the at least one of a plurality of particle physical characteristics from the determined velocity and a predetermined force field magnitude and direction.
These steps include several steps or sub-steps. In particular, the step of determining the velocity of at least one particle in a force field includes the step or sub-step of processing the at least two temporally defined digital images so that the particle is distinct from the background of each temporally defined digital image. This step of processing includes one or more of the following steps or sub-steps: histogramming, color stretching, filtering, background subtraction, identifying contrast differences. The step of determining the velocity of at least one particle in a force field further includes the step or sub-step of tracking the location of the particle through the at least two temporally defined digital images by determining at least one predicted path and the distance the particle has traveled. Other steps or sub-steps are more fully set forth in the detailed description.
According to another aspect of the present invention, a device for determining one or more particle physical characteristics is also described. More specifically, the device has a force field device for subjecting at least one particle to at least one force field, a substantially transparent flow channel, and a computer system for gathering and analyzing data associated with the at least one particle. The force field device has, among other things, a first and second force field producing assembly. Each assembly has a force field producing device and a pole piece for concentrating the force field flux. The pole pieces each have a flux concentrating portion having a curved end portion for producing a region of space having a substantially constant force field and wherein the flux concentrating portions are displaced substantially opposite each other with an inter-polar air gap therebetween. The substantially transparent flow channel is positioned at least partially within the region of space and provides for the introduction of at least one particle thereinto. A flow system having a pump for controlling flow into the channel is also provided.
According to another aspect of the present invention, a system for determining one or more particle physical characteristics is provided. The system has a force field device for generating at least one force field having a predetermined force field magnitude and direction and for subjecting at least one particle to the at least one force field, a flow system for regulating the introduction of the at least one particle into the force field device, and a computer system for gathering and analyzing data associated with the at least one particle. The computer system has, among other things, a digital image system for acquiring at least two temporally defined digital images of the at least one particle, logic for identifying and locating the at least one particle and its coordinates within the at least two temporally defined images, logic for determining the velocity of the at least one particle within the force field, and logic for determining at least one particle physical characteristic from the determined velocity and the predetermined force field magnitude and direction.
According to yet another aspect of the present invention, a pole piece assembly for producing a region of space having a substantially constant magnetic force field is provided. The assembly has, among other things, a first pole piece having a substantially curved flux concentrating portion, a second pole piece having a substantially curved flux concentrating portion, and a device for producing a magnetic flux in flux communication with the first and second pole pieces. The first and second pole pieces are configured to form an inter-polar air gap. The substantially curved flux portions of the first and second pole pieces each have a first distal end having a curved portion and a second distal end having a curved portion. The curved portion of the each first distal end includes a predetermined radius and the curved portion of the each second distal end includes an approximately hyperbolic function, wherein the hyperbolic function is defined by the function y(x)=9.544/x2xe2x88x9212.719, where x and y are Cartesian coordinates (preferably in millimeters) with the origin placed at the intersection of the plane of symmetry separating the pole pieces and a plane tangent to the radial portion of the distal ends of the pole pieces.
It is, therefore, an advantage of the present invention to provide an analytical tool for analyzing and measuring at least one of a plurality of particle characteristics.
It is another advantage of the present invention to provide a region of substantially constant magnetic force for application to at least one magnetically susceptible particle.
It is another advantage of the present invention to provide a computer system having logic for analyzing and measuring the magnetic susceptibility of at least one magnetically susceptible particle.
Further advantages will become apparent from a consideration of the ensuing description and drawings.